The proposed study will deal with the development of statistical models of the natural history of gynecological cancers including cancer of the cervix, uterus and breast. A clinical and histologic construct is provided as a theoretical model of the natural history of these malignant lesions which is a continuum partitioned into discrete transition states. The probability density functions that characterize the time or duration in each transition state, and the probabilities of transit from one state to another will be studied. The biological characteristics that are represented by the parameters of these functions will be determined. Estimates of these parameters for the population of interest and subsets of the population with differential relative risk will be computed. Using the results of these studies, we will investigated methods of evaluating the effects of the use of screening programs on the incidence, mortality and five year survival rates for each of the three lesions of interest. Using these indices the expected results of alternate screening strategies will be calculated and contrasted. These results will be used to compare the relative value of different cancer detection protocols in the individual and in the aggregate.